INTERACTION OF ALPHA-ACTININ WITH THE CADHERIN CATENIN CELL-CELL ADHESION COMPLEX VIA ALPHA-CATENIN

Cadherins are Ca2+-dependent, cell surface glycoproteins involved in c ell-cell adhesion. Extracellularly, transmembrane cadherins such as E- , P-, and N-cadherin self-associate, while intracellularly they intera ct indirectly with the actin-based cytoskeleton. Several intracellular proteins termed catenins, including alpha-catenin, beta-catenin, and plakoglobin, are tightly associated with these cadherins and serve to link them to the cytoskeleton. Here, we present evidence that in fibro blasts alpha-actinin, but not vinculin, colocalizes extensively with t he N-cadherin/catenin complex. This is in contrast to epithelial cells where both cytoskeletal proteins colocalize extensively with E-cadher in and catenins. We further show that alpha-actinin, but not vinculin, co-immunoprecipitates specifically with alpha- and beta-catenin from N- and E-cadherin-expressing cells, but only if alpha-catenin is prese nt. Moreover, we show that ol-actinin coimmunoprecipitates with the N- cadherin/catenin complex in an actin-independent manner. We therefore propose that cadherin/catenin complexes are linked to the actin cytosk eleton via a direct association between alpha-actinin and alpha-cateni n.